Electroencephalographic electrode



Feb. 10, 1959 J. E. ALDERMAN 2 ELECTROENCEPHALOGRAPHIC ELECTRODE Filed Nov. 20, 1957 E5 BY L4 770/?IVE Y.

United States Patent 2,872,926 ELECTROENCEPHALOGRAPHIC ELECTRODE Jerome E. Alderman, deceased, late of Syracuse, by Freida B. Alderman, executrix, Syracuse, N. Y.

Application November 20, 1957, Serial No. 697,610

1 Claim. (Cl. 128-410) This invention relates to electroencephalographic apparatus, and more particularly to an electrode therefor adapted for making electrical contact with the scalp.

In apparatus of the above type it is usual to make contact with the scalp of a patient undergoing examination at a number of locations suitably spaced from one another around the scalp. Seven, or thirteen or some other suitable number of contacts are made, and the slight variations in electrical resistance to current flow from one contact to the other, or the presence of electrical potentials between contacts are measured over a period of time and transcribed upon graphic charts. The charts of such currents are examined for the purpose of noting either the fact that the indications are normal, or the presence of any unusual disturbances or other indications of abnormalities. The making of a reliable stable contact to the scalp is of importance. Contact has been made by surface type electrodes comprising flat imperforate discs, and by non-surface type which require puncturing into the subcutaneous tissue of the scalp. Such contacts have resulted in unstable indications by reason of variations in contact resistance, difiicult to avoid in usage.

The present invention is directed to an electrode of circular concavo convex configuration, which when attached to the scalp with its concave face facing the scalp, forms a shallow cup for the reception of electrolyte adapted to make contact with the scalp over the definite circular area bounded by the circular rim of the electrode. The electrode is provided with a single central aperture affording access to the space defined by the concave face of the electrode and the embraced scalp area for clearing of foreign matter, and for the ready injection of suitable electrolyte paste into the space thus defined.

The above and other novel features of the invention will appear more fully hereinafter from the following detailed description when taken in conjunction with the accompanying drawings. It is expressly understood that the drawings are employed for purposes of illustration only and are not designed as a definition of the limits of the invention, reference being had for this purpose to the appended claim.

In the drawings, Figure l is a perspective view, enlarged, of an electrode applied to the scalp;

Figure 2 is a plan view;

Figure 3 is a side elevation; and

Figure 4 is a sectional view taken on the line 4-4 of Figure 2.

Referring to Figure 1, the electrode is shown as applied to the scalp S with its concave face facing the scalp. Such electrode has an exterior convex surface, generally spherical in shape and of a great circle diameter of about 60, that is, a great circle arc across the inside or outside face of the electrode may be about 60 in length, to provide the desired concavity. The electrode is provided with a single central aperture 12, a smoothly rounded edge 14, particularly on the inside face side 2,872,926 Patented Feb. 10, 1959 ice thereof. The electrode is also provided with a flexible electrical lead wire 16, which may be soldered to the electrode exterior, and additionally, if desired, may be looped through a pair of small apertures 18 and 20, in the annular region between the aperture 12 and rim or edge 14. The end of the wire after being looped through the apertures, may be twisted around the lead as at 22 to provide a measure of protection against breakage of the lead wire 16 due to fatigue from flexing adjacent its soldered connection. Where such apertures as 18 and 20 are provided, they are sealed by solder which flows and bonds the wire to the electrode where the wire passes through the electrode. The lead may be provided with a suitable connecting tip as at 24 at its other end.

In practice as many as 13 such electrodes may be applied to the scalp at various locations for a single examination and various connections made thereto. Each electrode before application is cleaned, and then held against the scalp at a point where the hair is parted to suitably expose the scalp, as by a prod 26 and while so held, an application of collodion is applied around the rim and the contiguous exposed scalp adjacent the rim. The prod may have an air tube 28 for delivering a light blast of air to the region to speed up the setting of the collodion. As soon as one such electrode is applied, and the collodion set sufficiently to hold, the application of other electrodes is made at other suitable points. The collodion seals the rim to the scalp and holds the electrode in place for the examination.

After all the electrodes are applied, the interior of each electrode may be lightly swabbed out by a small piece of cotton soaked with acetone, to remove any collodion which may be within the space defined by the electrode, and thereafter the electrode is filled with electrolyte paste, such as a mixture of bentonite powder, water and calcium chloride, the electrolyte being applied by a syringe or applicator tube, having a nozzle such as 30 capable of injecting the paste through the aperture 12 to fill the concavity within the electrode formed thereby together with the circular area of the scalp embraced by the electrode rim 14.

It will be seen that the concavity beneath the electrode affords an opportunity for insertion of electrolyte into the space embraced by the electrode whereby a circular contact area is established that provides a stable contact resistance or conductivity, and thereby facilitates the examination by reason of eliminating, so far as possible, the extraneous variations in conductivity manifested by other contact electrodes, whether of the surface, nonpuncture type or otherwise. When the examination is completed, the electrodes may be conveniently removed by softening the collodion with acetone.

In practice the electrode may have a diameter of about of an inch, and may be formed of brass, silver or other suitable material, and plated if desired to suit. Since the electrodes will be repeatedly used, it is desirable that the same be made of material as suggested so as to minimize corrosion and facilitate cleaning.

Although a single embodiment of the invention has been illustrated and described, it is to be understood that the invention is not limited thereto. As various changes in the construction and arrangement may be made without departing from the spirit of the invention, as will be apparent to those skilled in the art, reference will be had to the appended claim for a definition of the limits of the invention.

What is claimed is:

An electroencephalographic electrode comprising a circular rigid disc of conductive metallic material, convex on its outside face and concave on its inside face, said disc being formed of substantially uniformly thick 2,872,926 3 4 sheet material and being substantially a circular segment area of the convex face of the disc intermediate said rim of a spherical surface having an arc diameter of about 60, and aperture. said disc having a smooth rounded rim edge and having a single central aperture through which may be injected References (3295 in the file of this P an electrolyte paste, and said disc having a flexible lead 5 UNITED STATES PATENTS wire bonded thereto, and leading away from an annular 2,580,628 Welsh Jam 1, 1952 

